Submersible motor with mercurysealed balancing means



May 28, 1935. E. MENDENHALL ET AL 2,002,910

SUBMERSIBLE MOTOR WITH MERCURY SEALED BALANCING MEANS Original Filed Nov. 7, 1927 2? Sheets-Sheet l & H n. P N a w Nam W 7. 7 T M M W0 d m Wm M. x f 5 W 0 7 m flfl m 4 56 1 May 28, 1935. E. MENDENHALL EI'YAL SUBMERSIBLE MOTOR WITH MERCURY SEALED BALANCING MEANS Original Filed NW. 7, 1927 2 Sheets-Sheet2 17/ yam/70%; far/ M60061? ha 1/6/0106 1/ 6 0/ 1? Y M E" 5 4k Patented May 28,1935

UNITED STATES SUBMERSIBLE MOTOR WITH MERCURY- SEALED BALANCING MEANS Earl Mendenhall and Junius B. Van Horn, Los

Angeles, Calif., assignors to Menhorn, Inc., Los Angeles, Calif., a corporation of California Application November 7. 1927, Serial No. 231,513 Renewed August 3, 1932 17 Claims.

Previous attempts to operate a motor submerged in a fluid have not been entirely successful due to the difl'iculty of keeping the windings of the motor dry and preventing any of the external fluid from reaching the windings of the motor. We have found that these problems are completely solved by filling the shell of the motor with an internal neutral fluid which is non-injurious to the windings, this fluid having a low viscosity, high dielectric strength, and being a good lubricant for the bearings.

It is, of course, necessary to prevent any admixing of the internal and external fluids if the latter is to be kept from the bearings of the motor. Ordinarily the greatest tendency toward admixture will be at the junction of the shaft and the motor shell and we have found that by placing a suitable fluid-packed seal at this junction we can effectively prevent any admixture of the internal and external fluids.

Such a fluid-packed seal can most conveniently be formed by using a body of mercury to separate the internal and external fluids. Such a body of mercury has one surface in contact with-the external fluid and another surface in contact with the internal fluid. Thus, should any diiference in the pressures of the two separated fluids exist, there will be a tendency to force the mercury out of its sealing relationship and allow an intermixture of the fluids. It is thus desirable to efiect a substantial equalization of the pressures of the fluids. One system of eifecting this result is by the use of a balance chamber in which bodies of internal and external fluids are in contact. Such a system is shown and claimed in our copending application Serial No. 114,414, filed June 8, 1926, now Patent No. 1,879,625. Another system of thus substantially equalizing the pressures is to use a flexible diaphragm or bellows, such as disclosed and claimed in our copending application Serial No. 217,688, filed September 6, 1927.

In order to so equalize the pressures of the internal and external fluids in the instant application, we have found. it advantageous to use a separating member, opposite sides of which are in contact with the internal and external fluids. This separating member must be movable in order to efiect an equalization of pressures, and we have found it desirable to keep the edges of the separating member below the surface of bodies of mercury or other sealing fluid, allowingthe member to move. relative to the mercury.

It is an object of our invention to provide an improved motor which can be operated submerged in a fluid which might be injurious to the working parts of the motor should it enter therein.

Another object of our invention is to provide a shell which may enclose such a motor or other device, this shell containing an internal neutral fluid and equipped with fluid-packed devices for preventing any admixture of the 1 external and internal fluids.

Still a further object of our invention is to provide such a shell in which the pressures of the internal and external fluids are equalized to prevent the separating fluid in the fluid-packed devices from being displaced to, in turn, prevent an inter-mixture of the internal and external fluid.

It is desirable to be able to supply additional internal fluid to the interior of the motor after the motor has been submerged. We provide a supply pipe adapted to supply this internal fluid to the shell, the separating member moving to allow for this added fluid and displacing a portion of the external fluid in so doing. Should the separating member be moved into a maximum position, it is desirable to provide a path of escape of the internal fluid into the external fluid.

It is a further object of our invention to provide a separating member separating an internal fluid in a submersible motor shell from an external fluid surrounding the motor shell, this separating member being movable between maximum positions and allowing a passage of internal fluid into said external fluid when the member is in a maximum position, but impeding any reverse passage of said fluids. The combination of a pressure release means and a fluidpacked sealing means is shown and claimed in 40 our copending application Serial No. 255,544, filed February 20, 1928.

Still a further object of our invention is to provide a mercury-sealed separating member, the mercury being displaceable under suflicient difference in pressures of the fluids to allow one of the fluids to bubble therethrough, this displacement taking place relatively easily to allow a passage of said internal fluid into said external fluid, but greatly impeding a reverse passage.

In lowering the motor into the external fluid, it is desirable to prevent the interior fluid from escaping. We accomplish this by means of a pipe which joins to the bottom of the motor shell and extends to a point near the top there- 55 of, this pipe maintaining a fiuid in static balance with the internal fluid until the motor is completely submerged.

It is an object of our invention to provide a device which will prevent the escape of any internal fluid in a motor shell while the motor is being submerged.

Further objects and advantages of our invention will be made evident hereinafter.

We have illustrated one form of our invention with particular relation to the deep-well pumping art, but it is to be understood that this embodiment is for illustrative purposes only, and we do not limit ourselves to'the use of the invention in this connection.

Fig. 1 shows one application of the motor of our invention. 3

Fig. 2 is a vertical cross-sectional view of the submersible motor of our invention.

Fig. 3 is an enlarged sectional view of a portion of Fig. 2.

Fig. 4 is a cross-sectional view taken along the line 6-4! of Fig. 2.

Figs. 5, 6, '7, and 8 are vertical cross-sectional views of the fluid-packed rotary seal.

Fig. 9 is a horizontal cross-sectional view taken on the line 9--9 of Fig. 2.

Fig. 10 is an alternative form of our invention.

Referring in particular to the drawings, Fig. 1 shows a well 55. Extending into the well is a discharge pipe I6 carrying at its lower end a pump unit H. The upper end of the discharge pipe I6 is connected to an elbow 38 which communicates with a secondary discharge. pipe I9. The motor 20 of our invention is suitably secured in the discharge pipe l6 and is adapted to rotate the impellers (not shown) of the pump unit I? to raise water or other external fluid in the well to the surface of the ground.

Fig. 2 most clearly shows the details of the motor of our invention. The motor 20 is surrounded by a shell 22 which is closed at its lower end by a bottom member 23 suitably secured to the shell by screws 25. Closing the upper end'of the shell 22 is a top member 2'8 which is suitably secured to the shell, such as by welding indicated at 28. Extending upward from the top member 2? is an oil-supply pipe 30. This oil-supply pipe extends upward throughout the well and through the elbow I8 at the surface of the ground. Connected to the pipe above the elbow I3 is a pipe 32 having a valve 33 therein. The pipe 32 is connected to a suitable oil-pressure source. The oil-supply pipe 30 is also adapted to carry insulated leads 35 which extend through a pothead 36 at the top of the oil pipe 30. These leads 35 are adapted to supply electrical current to the windings of the motor 20.

Tightly fitting in the shell 22, and suitably held in place therein, is a stator 38 of the motor 20 having longitudinal grooves 39 spaced around the periphery thereof. These grooves 39 communicate between an upper chamber 40 above the stator 38 and a lower chamber below the stator 38. The stator 38 has windings M to which the leads 35 are connected.

Supported on the upper end of the stator 38 below the stator 38 is an intermediate bearing member 44, the upper and intermediate bearing members being suitably secured to the stator by bolts extending through each bearing member and the stator 38. Upper and intermediate bearings 41 and 4B are carried respecings 41 and 48. A cylindrical bafii'e 54 having openings 55 therethrough extends between the intermediate bearing member 34 and the lower bearing plate 50. The lower bearing plate 50 has openings 56 therethrough, these openings communicating with the space surrounding the bailie 53.

A shaft 5'? extends through the bearings 84, 68, and 52 and extends downward through an opening 58 in the bottom member 2 5. A rotor 39 is secured to this shaft, this rotor being adapted to rotate in an opening 60 of the stator 33, there being a gap GI between the rotor and the stator.

The lowerbearing plate 33 divides the shell 22 into a main or motor chamber 33 and a separating chamber 6 3. A fluid-packed seal 85 of our invention is positioned in the separating chamber t l. This seal 35 comprises a supporting structure 33 which has a, lower cylindrical portion lil engaging a boss ll of the bottom member 24. An openinglZ is formed through this lower cylindrical portion at a point just above the boss 'I i. Extending across the upper end of the lower cylindrical portion 53 is a radial wall l5, and extending upward from this wall is a shaft-enclosing tube 16. This shaft-enclosingr tube is concentric with the shaft 51, but spaced a distance away from the outer periphery thereof, and-securely fits in a recess '53 in the lower bearing plate 50.

Also extending upward from the radial wall 75 is a cylindrical wall 8i which is concentric with the shaft-enclosing tube 56, but spaced a distance therefrom. The wall BI and the tube I3 form an inner annular mercury chamber 83. Webs 33 extend outward from the cylindrical wall 3! and support at their outer ends a largerdiameter cylindrical wall 86. Of still greater diameter than the wall 86 is a cylindrical wall 88 which securely engages the inner periphery of the shell 22. The walls 36 and 88 are joined at their lower ends by a plate 89, these three elements defining an outer annular mercury chamber 90. The inner and outer annular mercury chambers 83 and 98 respectively are substantially half filled with mercury, as clearly indicated in Figs. 2 and 3.

Adapted to extend below the surface of the mercury in the chambers 83 and 99 are cylindrical side members members forming a part of a separating member I04 of our invention. The upper ends of the cylindrical side members I00 and IOI are joined by an upper annular wall I06. The separating member I04 is adapted to slide vertically in the separatingchamber 6 3. This separating member I 04 at all times divides the separating chamber 64 into an internal-fluid chamber I09 and an external-fluid chamber IIIl spaced re- Ifill and IN, these side spectively above and below the separating mem- Communicating between the chamber III) and the external fluid in the well is a filling pipe H3 which extends upward along the exterior of the shell 22 to a point a short distance above the topplate 21.

Formed in the upper annular wall I05 is an opening H5. In the center of this opening is a guide H6 held in place by ribs H1. Extend ing through an opening in the guide H6 is a stem H9 of a poppet valve I2I. The poppet valve is adapted to engage a seat I22 of the upper annular wall I06 in a manner most clearly shown in Fig. 3. A spring I25 keeps the poppet valve I 2| in fluid-tight engagement with the annular wall I06. This valve is operable when the separating member I04 is in a lowermost position to allow a passage of fluid from the chamber I09 into the chamber H0, should the pressure in the former chamber become greater than the pressure in the latter. The converse is not true, however, for should the pressure in the chamber H exceed the pressure in the chamber I09, the valve would not open. The fluid-packed seal of our invention also comprises a means for allowing fluid to escape from the chamber I09 into the chamber H0, or vice versa, by bubbling through the mercury, such a passage of fluid taking place only under exceptional circumstances, as will be more clearly brought out in the operation of the invention. It should be noticed that the cylindrical side member IN is not centrally spaced in the annular mercury chamber 90, but is spaced closer to the wall 80 than to the wall 86. Similarly, the cylindrical side member I00 is spaced closer to the shaft-enclosing tube 16 than to the wall BI.

The separating member I04 adapted to be slidable to equalize the pressures between the internal fluid in the chamber 509 and the external fluid in the chamber H0 and to separate these two fluids, but should any unequalized difference of pressure exist between the chambers I09 and H0, it is clear that the mercury in the annular chambers 83 and 90 would be displaced in proportion to the amount of diiference in pressure. Should the pressure in the chamber H0 exceed that in the chamber I00, the mercury level III would be lowered and the mercury level I I2 would be raised. Similarly, the level H3 would be lowered and the level H4 raised. Should the pressure in the chamber H0 be sufiiciently greater than the pressure in the chamber I09, the levels III and H3 would be lowered into positions indicated at I30 and I3I. Simultaneously, the levels H2 and H4 would be raised to levels indicated by numerals I32 and I33 in Fig. 3. At this time fluid would, of course, escape from the chamber H0 around the lower edges of the side members I M and I00, this fluid reaching the chamber by bubbling through the mercury surrounding the cylindrical side members. Conversely, if the pressure in the chamber I09 became sufficiently greater than the pressure in the chamber H0, the levels H2 and H4 would lower into positions indicated at I35 and I36 of Fig. 3. At this time the levels III and H3 would rise into positions indicated at I31 and I30. It should be noted that the difierence in pressure in the former case would be much greater than the difference in pressure in the latter case, due to the difierence in cross-sectional areas of the mercury chambers on either side of the side walls, so that it would be much easier for fluid to escape Into the chambm' H0 is normally than into the chamber I09. This differentialrelease feature of our invention is particularly applicable in certain installations and might be used to entirely eliminate the poppet valve I2i. The lower cylindrical portion and the radial wall define a sealing chamber I49 in which is supported a rotary fluid-packed seal I50 of our invention. This seal is best illustrated in Figs. 2, 5, 6, 1, and 8. The rotary seal comprises an apron I5I secured to, and extending downward from, the radial wall 15. This apron is concentrio with the shaft 51 and diverges at its lower end therefrom. A radial flange I52 is formed on the extreme lower end of the apron I5I. Suitably secured'to the shaft 51 is a cup I55 which is adapted to be substantially half filled with mercury. The lower end of the apron I5I and the radial flange I52 are adapted to extend below the surface of the mercury in. the cup I55. The cup I55 has a cover I50 having a clearance space I59 between the outer edge of the apron I 5I and an opening I60 through the cover I58.

When in a stationary position, all pressures being equalized, the mercury in the cup I55 stands at the same level I02 in the space I62 surrounding the apron and in the space I63 between the apron I5I and the shaft 51. The level in the space 563 is indicated by the numeral IE4. levels I62 and I64 assume the paraboloid shape shown in Fig. 6, but it should be noticed that the outer edges of the radial flange I52 are always beneath the surface of. the mercury regardless of the rotation of the shaft.

The space I63 is indirectly in communication with the chamber I09 through the bearing 52 and the openings 55 and 50. The level I02 of the mercury in the cup I 55 is in communication with the chamber H0 through the clearance space I50 and the opening 12. Thus, if the pressure in the chamber I 09 became sufficiently greater that the pressure in the chamber 6 I0, the surface I64 would be lowered into a position indicated by the numeral I69 of Fig. 8, while the level I62 would be raised into a position indicated by the numeral I10 of the same figure. In this position, fluid would escape from the chamber I09 into the chamber H0 by bubbling through the mercury. Conversely, if the pressure in the chamber H0 were greater than the pressure in the chamber I09, the level I62 would be lowered into a position indicated by the numeral I12 of Fig. 7, and the level I64 would rise into a position indicated by the numeral I13 of the same figure. In this position, fluid might escape from the chamber H0 into the chamber I09. It will be noticed that the rotary seal of our invention also has the differential-pressurerelease feature, and that it is much easier for fluid to escape from the chamber I09 into the chamber H0 than it is for the fluid to pass from the latter chamber into the former, the pressure difference in the former case being proportional to the distances between the levels I09 and I10 and in the latter case being proportional to the distance between the levels I12 and I13.

It will be noticed that the fluid-packed seal 65 and the rotary fluid-packed seal I50 are both displaced by any difference of pressure which might build up between the chambers I09 and When the shaft is rotating, the

H0. In the form of the invention illustrated in- Fig. 2, however, it is extremely improbable that an? fluid will escape either around the cylinpipe III-l will increase.

drical side members I or IM or around the outer edges of the radial flange I52. This is because of the fact that if the pressure in the chamber I I0 were to be increased over the pressure in the chamber I00, the separating member I04 would be raised from its full line position shown in Fig. 2 toward its dotted line upper position indicated by the numeral I19. The separating member I04 will, of course, only ri'se until the pressure in the chambers I09 and IN are equalized. The normal operating position of the separating member I04 is near its lowermost position, as will be brought out in the operation.

In assembling the motor of our invention, the mercury chambers are filled with a proper amount of mercury. Before lowering the motor beneath the surface of the fluid in which it is to be submerged, it is desirable to fill the motor chamber 63 with a suitable oil or other internal fluid having suitable characteristics. This is most conveniently accomplished by pouring into the filling pipe 3 a suflicient quantity of the external fluid to cause the separating member I04 to assume its dotted line position I10, as indicated in Fig. 2. At the same time the interior fluid is supplied through the pipe 30. This fluid passes through the grooves 39 of the stator 30 and through the bearing 52 and into the space I63 of the rotary fluid-packed seal. This internal fluid also flows through the openings 55 and 56 thereby reaching the internalfluid chamber I09. As more of the internal fluid is poured into the oil-supply pipe 30, the

motor chamber 63 becomes filled with oil and the separating member I04 is forced into its lowermost position. Reaching this position, any excess of internal fluid will operate the poppet valve IZI and will discharge into the chamber H0. It should be understood that as the internal fluid forces the separating member I04 downward some of the external fluid previously poured through the filling pipe H3 will discharge from the top ofthis pipe.

It is preferable to submerge the motor when the separating member I04 is in its lowermost position. This is most clearly explained by considering the fact that as the motor is lowered the fluid pressure on the fluid in the filling This will force the separating member I04 upward, thus raising the level of the oil in the oil-supply pipe. The internal-fluid level in the pipe 30 will be substantially the same as the level of the external fluid in the well if the valve 33 is open, for a rise of one inch of the separating member I 04 will cause a rise of many feet in the oil tube 30, due to the large differences in cross-sectional area. When the motor has been lowered into its proper position, the leads 35 are supplied with electrical potential to operate the motor 20.

-If used in an installation as indicated in Fig. 1, it will be apparent that when the motor is set into operation the pump I! will force the fluid upward in the discharge pipe I 6, thus increasing the pressure on the fluid in the filling pipe I I 3 and thus tending to raise the internalfluid levelin the oil-supply pipe. It is therefore preferable to force an excess of internal fluid through the oil-supply pipe 30 at this time, thus completely filling this pipe, at which time the valve 33 may be closed. If it is desired to force more internal fluid into the motor when it'is operating under the conditions shown in Fig. 1, it will be necessary to force this fluid 'lowingfluid to easily pass from the chamber I09 into the chamber IIO, but requiring a larger difference in pressure to reverse this flow. This, of course, is desirable inasmuch as it would be extremely detrimental to the working parts of the motor to have any of the external fluid enter the chamber I09 and the motor chamber 63.

It should be noticed that in the preferable form of the invention shown in Fig. 2, an excess,

of pressure in the chamber I09 over that in the chamber III) would have three paths of escape, should the separating member I04 become caught or otherwise rendered inoperative. The excess pressure could be relieved through the fluid-packed seal 65, or through the rotary fluidpacked seal '10, or could pass through the poppet valve IZI. Thus, it should be apparent that it is not'absolutely necessary to use a poppet valve I2I of the type prescribed. We prefer to use this triple combination to entirely obviate any possibility of any of these paths becoming inoperative. The poppet valve IZI is so designed that it will first release the excess of pressure in the chamber I09. It is immaterial which of the mercury seals is used to release this pressure in the event the poppet valve IZI should fail. I

It should thus be apparent that our invention would be operative even though the separating member I04 should be secured rigidly in place. We have shown such an embodiment of our invention in Fig. 10 in which the separating member I04 is secured to the shaft-surrounding tube' 07 by means of a bracket I85. In this embodiment of our invention we rely entirely upon the differential-release feature of the mercury seals of the invention allowing any excess of pressures to be relieved by fluid bubbling through the mercury. This embodiment of our invention is open to the objection that it is extremely dificult to keep all the external fluid out of the motor chamber 63 unless enough internal fluid is forced through the pipe to always keep the pressure in the chamber I09 greater than the pressure in the chamber IIO.

We claim as our invention:

1. In a device adapted to operate below the surface of an external fluid, the combination of:

a shell, the interior of said shell containing an internal fluid; a fluid-sealed member separating said internal. and said external fluids; and a,

internal fluid; a fluid-sealed member separating said internal and said external fluids; and'apressure-operable check valve in said member, said valve allowing a passage of fluid in only one direction therethrough when the pressure in a primary liquid, the combination of: a shell adapted to be submerged in a primary liquid;

walls forming a separating chamber communicating with a secondary liquid in said shell and with said primary liquid; a member separating said liquids in said separating chamber and movable through a limited path of travel to substantially equalize the pressures of said liquids; and a pressure release means for releasing a difference in pressure which may exist between said liquids in said separating chamber when said member is at the end of its path of travel.

5. In a submersible structure, the combination of: a shell; walls associated with said shell and defining a channel containing a body of sealing liquid, said walls including a pair of vertically extending side walls; and a separating member extending vertically downward into said channel and below the surface of said sealing liquid, one side of said member communicating with the interior of said shell and the other side communicating with the exterior thereof, said member lying closer to one of said side walls than to the other whereby said sealing liquid is differentially displaceable by a difference in pressure existing between the interior and exterior of said shell.

6. In a structure adapted to operate surrounded by a fluid, the combination of: a shell containing a lubricating medium; a rotatable shaft extending from said shell; a fluid-packed seal sealing the junction of said shaft and said shell; and a vertically-movable fluid-packed member separating said fluid and said lubricating medium and transferring pressure therebetween.

7. In a structure adapted to operate surrounded by a fluid, the combination of: a shell containing a lubricating medium; a rotatable shaft extending from said shell; a fluid-packed seal sealing the junction of said shaft and said shell, said seal comprising a body of sealing liquid around said shaft and an apron dipping thereinto and separating said fluid and said lubricatingmedium whereby said sealing liquid is displaceable by a pressure difference existing between said fluid and said lubricating medium; walls forming a separating chamber containing a body of sealing liquid, said separating chamber having access to said lubricating medium and to said fluid; and a member movable in said separating chamber and dipping into the sealing liquid therein, said member separating said lubricating medium and said fluid in said chamber and being movable to substantially equalize the .pressures thereof.

8. In a structure adapted to operate surrounded by an .external liquid, the combination of: a shell containing an internal liquid; 2. rotatable shaft extending from said shell; a seal for sealing the junction of said shaft and said shell; and walls defining a separating chamber in said shell and communicating with said internal and able shaft.

9. A combination as defined in claim 7 in which both of said bodies of sealing liquid are displaceable to allow a passage of lubricating medium or fluid therethrough upon the occurrence of a sufficient pressure differential between said lubricating medium and said fluid, and including a valve means operable to release such a differential pressure before it becomes large enough to effect such passage through either of said bodies of sealing liquid.

10. In combination: walls forming a separating chamber communicating with internal and external fluids; walls forming a pair of annular chambers in said separating chamber, said chambers being concentric relative to each other and each containing a body of sealing liquid; and a separating member separating said fluids in said separating chamber and providing inner and outer concentric cylindrical side walls respectively dipping into said bodies of sealing liquid and joined at their upper ends by an upper wall of annular shape.

11. In a device adapted to operate below the surface of a primary liquid, the combination of:

a shell containing a secondary liquid and providing a separating chamber communicating with said primary and secondary liquids and containing bodies of these liquids; a rotatable shaft extending from said shell; sealing means for sealing the shaft with respect to said shell; walls in said separating chamber defining an annular channel containing a body of sealing liquid; and a pressure equalizing separating member vertically movable in said separating chamber and providing a vertically extending side wall dipping into said body of sealing liquid, said separating member and said sealing liquid separating said liquids.

12. In a-submersible structure adapted to be submerged in an external liquid, the combination of: a shell providing a chamber containing a body of internal liquid; a supply pipe communicating with said chamber and extending upward to a point above the surface of said external liquid; a shaft extending from said shell; a seal between said shaft and said shell and separating said internal and external liquids; means for admitting said external liquid into said shell for substantially equalizing the pressures on opposite sides of said seal and forcing said internal liquid upward in said supply pipe until the pressure therein at the point of communication with said shell equals the pressure in said shell; and means closing the upper end of said supply pipe.

13. In a submersible structure, the combination of a shell submerged in an external liquid and defining a chamber containing an internal liquid; a shaft extending through said shell; a fluid-packed seal for sealing said shaft relative to said shell and including a body of sealing liquid separating said internal and external liquids; means for admitting said external liquid into said shell for substantially equalizing the pressures acting on opposite sides of said seal; a surge-compensating means including a supply pipe communicating with said internal liquid in said shell and in which said internal liquid rises under the influence of said first-named means until a pressure head is demovable pressure-trans-.

sure in said shell, an increase of the pressure of said external liquid outside said shell thus tending to force more of said internal liquid into said supply pipe; and means closing the upper end of said supply pipe to control the pressure above the column of said internal liquid in said supply pipe, thus controlling the amount of said internal liquid entering and leaving said supply plpe. r

14. In a structure adapted to operate surrounded by an external liquid, the combination of: a shell containing an internal liquid; walls in said shell defining a main chamber substantially filled with said internal liquid; a shaft means extending from said main chamber to a point outside said shell; a seal at the junction of said shaft and said shell; walls in said shell defining a space vertically disposed relative to said main chamber and containing a body of a third liquid spaced from said shaft means and providing two separated surfaces, one of said surfaces communicating with said internal liquid; and means communicating between the other of said surfaces and said external liquid' whereby the pressure on said other of said surfaces varies in response to pressure changes of said external liquid and whereby said body of third liquid efiectively separates said internal and external liquids.

15. In a structure adaptedxto operate surrounded by an external liquid, the combination of: a shell containing an internal liquid; walls insaid shell defining a main chamber substantially filled with said internal liquid; a shaft means extending from said main chamber to a point outside said shell; a seal at the junction of said shaft and said shell; stationary walls defining a U-shaped space containing a U-shaped body of a third liquid in said shell and vertically disposed relative to said main chamber and providing separated surfaces, one of said surfaces communicating with said internal liquid; and means communicating between the other of said surfaces and said external liquid whereby the pressure on said other of said surfaces varies in response to pressure changes of said external liquid, said U-shaped body of said third liquid being thus between the internal and external liquids but being displaceable upon relative change in the pressures on said separated surfaces.

16.111 a structure adapted to operate surrounded by an external liquid, the combination of: a shell including a main chamber substantially filled with an internal liquid; walls in said shell defining a separating chamber vertically disposed relative to said main chamber and communicatingat one position with said external liquid and at another position with said internal liquid; means in said separating chamber for separating said internal and external liquids, said means including a body of a third liquid and a movable separating member associated withpsaid body of third liquid and movable when the pressure of said external liquid changes relative to the pressure of said internal liquid; and a shaft means extending from said main chamher and from said shell.

17. A combination as defined in claim 16 including a fluid-packed seal sealing the junction of said shaft and said shell and providing a body Of\ a sealing liquid displaceable by a pressure difierential between said internal and external liquids.

' EARL mNDENI-IALL.

JUZNTUS B. VAN llORN. 

